Oxidation of olefins to unsaturated aldehydes



I OXIDATION 015 on to passing the olefin'va'pors admixed with molecular oxygen Unite Stats Patent 9 Claims.

This invention relates to an improved process for the oxidation of olefins to unsaturated aldehydes and is acontinuation of our co-pending application Serial No. 616,-

600 filed October 18, 1956, and now abandoned.

Olefins have been oxidized in the prior art by methods which comprise reacting the olefin, such as propylene,

yvith agas containing molecular-oxygen to form the corresponding aldehyde in which metal selenites and tellurites are used as catalysts. Although almost any metal selenite or tellun'te may be used, silver selenite is preferred. The life of'eventhe'preferred'catalyst is very limited. In fact,

its catalytic activity decreases almost 'to zero in a very short 'tirne.

The activity of such 'a catalyst may be improved by incorporating therein an oxide of 'copperQmanlg'aiiesefnickel, or zinc. When this is done, the activity of the catflyst decreases rapidly at first but not to zero "and then more slowly. As a result, the catalyst containing the promoter remains active even though such activity is limitedbver a relativelylong period of time. an

proveiiieiit'ih this process,it has beenproposed (as' 'fo'r amPIeUQS. Patent 2,670,379) to oxidize anolefin by over a copper containing catalyst in thep're'senceof elementary'selenium. Theselenium can'be introduced as vapor orproduced in situ by decomposition of a decomposible selenite under the reaction conditions. While this latter process is rather eflicient and good yields of thedcsired product can be obtained, the use of selenium is undesirable. Selenium is expensive, and its vapors are toxic which makes it imperative that the selenium be recovered virtually completely from the efliuent gases before they are discharged to the atmosphere. Since selenium is not readily removed from the efiiuent gases by use of solvents,

or agents, such asalkalis, acids, or oxidizing agents, resort to special techniques must. be made'which add considerably to the cost of operation.

It'is, therefore, a principal object of the present invention to provide a process which obviates the disadvantages of theprior art' processes. It is another object of our invention to provide the process for the oxidation of olefins to unsaturated aldehydes utilizing a catalyst which will maintain its activity over long periods of time. It is a further object of the present invention to provide a cat alyst for the oxidation of olefins to unsaturated aldehydes which is low in cost and does not have objectionable toxic characteristics. These and other objects and advantages of the present process will be apparent as the invention is hereinafter morefully described.

'To t'he accomplishment of the foregoing-and related ends, this invention then comprises the features hereinafter fully described and particularly pointed out in the ice claims, the following description setting;- forth certain illustrative embodiments of the invention. These features are indicative, however, of but a few of the variousways in which the principle of the invention-may be employed. g n 7 g Broadly stated, the present invention comprises a method whereby anolefin of the general formula 1 wherein the R is selected from the group consistingof hydrogen andalkyl radicals is passed over -a copper silicate catalyst-admixed with molecular oxygen and,-in-the:presence of sulfur, whereby the olefin is oxidized to the-cor- "responding unsaturated aldehyde.

Before-proceeding ,with the specific example illustrating our invention, it may be well to indicate ingeneral the types of compounds required in the process.

*Olefinsthatmay beoxidized to the corresponding aldehyde include propylene, isobutylene, -2em'ethylbutene-l, Z-methyl penten'e-l, 2;3-dimethyl butene-1,"2-methyl The solid contact catalystwhich may be used is preferably amass-containing as a-catalytic substance copper silicate. The-catalytic substance may be distributed upon "carriers, such as purnice, asbestos, silica gell, andalumina,

in order to obtain alarge area of active -surface or the catalytic substance may be used-in the form'of pellets.

The sulfur acting in conjunction -with-the---contaot-cat alyst may be added to the'mixture ofgaseousreactants 'in the form of vaporyorit may be generated in situ by thedecomposition of decomposable sulfides which maybe present in-the catalytic substances described above. -Suitable sulfides include those of -copper, silver,-antimony, bismuth, and iron. When thesulfur is supplied in the form of vapor admixed with the gaseous reactants, it is expedient'to pass part "or the wholeofthe olefin oxygen mixture orcven part orthe whole'of theolefins only. over theheated Bya'djusting the temperature at 'which the gas or the gas" mixture is passed over the'sulfur and/01' by regulating the amount of gas passed over :the sulfur,

5 the amount ofsulfur inthe gas m'ixturemay be regulated. .4

When sulfur is added inthe vapor formto the gaseous reactants, its amount can vary within wide limitsand depends to a certain extent on the nature of thecontact catalyst used and the olefin to be oxidized. Thus,'to oxidize isob'utylene, there may be used from about 0.01to about 2.0- gramsof sulfur per *lite'rs of a gas-mixture'conta'ining 2 percent by volumeofisobutylene. More than 2.0 grains may be used, but the reaction'the'n becomes complicated by the formation ofsulfur containing compounds resulting from the reaction of -isobutylene -and methacrolein with sulfur dioxide. I'he'preferred-rangeof sulfur concentration is from about 0.1 to about-1.0: gram of' sulfur per IOU-liters of *gas containing 2 "percenciso- -butylene measured under standard conditions.

The molecular oxygen'containing gas that-mayc'be-used in-process of this invention may be air, 'air fortifid with oxygen, or oxygen. The molecular-oxygen containiiigtgas may be diluted with inertgases such as, for example, can box dioxide, nitrogen, or steam. I

Diluen'ts' such as carbon dioxide and steam have the added advantages that they can readily be removed from the effluent gas stream by scrubbing or condensation.

The ratio of oxygen to olefin that may be used varies over a wide range. Thus, from about 0.01 to 100 parts of air per part of olefin may be used; however, since the olefins form explosive mixtures with gases, it is probably advisable to avoid certain concentrations. With air and olefin mixtures, the explosive range is from 7 to 70 parts of air per part of olefin. Therefore, ranges free from the hazard of explosions that may be used in the .processjof this invention are from about 0.01 to 7 parts of-air-per paitof olefin and from 70to 100 parts of per part of ollefin. With air and propylene mixtures,

the explosive range is from .8 to 49 parts of air per part of propylene; and with air and isobutylene mixtures, the explosive range is from 9 to 60 parts of air per part of isobutylene. In general, the higher the molecular weight of the olefin, the broader is the explosive range. For oxygen containing gas mixtures containing higher concentrations of oxygen than air, the explosive range is broader than the range for air; and for mixtures containing lower concentrations of oxygen than air, the range is narrower.

The oxidation reaction of this invention may be carried out under reduced pressure or at super-atmospheric pressures.- The preferred pressures are from atmospheric to 2 or 3 atmospheres. In general, the explosive range as described above for olefin-oxygen containing gases is narrower for reduced pressures and broader for elevated pressures.

The temperature range in which the oxidation reaction of this invention may be carried out is from about 180 to 400 0., preferably from 275 to 350 C.

. The unsaturated aldehydes produced by the oxidation reaction may be recovered from the reaction mixture in any suitable way, for instance, by scrubbing with a solvent or by cooling. The scrubbed gas mixture may be allowed to go to waste, particularly when it contains only a small percentage of olefin or it may be replenished with olefin and oxygen and recycled.

In order to disclose the nature of the present invention still more clearly, the following illustrative examples will be given. It is to be understood that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as such limitations are specified in the appended claims. Parts where used are parts by weight.

Example 1 A solution of 242 parts of Cu(NO -3H O dissolved in 1,000 parts of water was slowly added to a solution of 142 parts of sodium nietasilicate, Na SiO -9H O in 2,000 parts of 'water while stirring the mixture rapidly. The light blue'precipitate which was produced was filtered, drained dry, and dried at 100- C. The product was further heated in a stream of air for 1 /3 hours at 300 C., machine pelleted x ,1 and activated by heating at 600 C. for 1 hour.

U-shaped reactor tube of Pyrex glass having a 9 'mrnboreand a length of 35 cm. was charged with 20 g. of catalyst pellets and heated in a liquid bath at 320 C. A 10 liter per hour'stream of an air-isobutylene mix- :ture containing 2 percent of isobutylene (1 part isobutylene to 49' parts air) was divided into two streams, one stream of which was passed through a vessel containing molten sulfur heated at such a temperature that 0.009 g. per hour of sulfur volatilized. The two streams were then-combined and passed into the reactor tube. The exit gases from the reactor tube were scrubbed with water to remove methacrolein. After 24 hours, it was found that 13.0 percent of the isobutylene feed had been converted to methacrolein and 2.0 percent to carbon dioxide.

Example 2 1 Example 1 was repeated with the exception that no sulfur was introduced into the system. After 24 hours, it

4 was found that 1.0 percent of the isobutylene had been converted to methacrolein and 0.5 percent to carbon dioxide.

I Example 3 Example 1 was repeated with the exception that 0.1 g. of sulfur was introduced into the system instead of 0.009 g. of sulfur. After 24 hours, it was found that 16.7 percent of the isobutylene had been converted to methacrolein and 2.5 percent to carbon dioxide.

Example 4 Example 1 was repeated except that propylene was used instead of isobutylene. It was found that 15 percent of the propylene had been converted to acrolein and 3 percent carbon dioxide. I

Example 5 Example 4 was repeated except no sulfur was used in the reaction. Less than 2 percent of the propylene was converted to acrolein and 1 percent to carbon dioxide.

Example 6 s Example 7 Example 6 was repeated except no sulfur was introduced into the system. Only 1 percent of the Z-methylbutene-l was converted to a-ethylacrolein and 2 percent to carbon dioxide.

Similar results were obtained when cupric, silver, antimony, and ferric sulfides were each substituted for elementary sulfur. When these decomposable sulfides were used, they were added to the copper catalyst.

While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto, since many modifications may be made; and it is, therefore, contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

We claim:

1. A process for the preparation of alkyl substituted acroleins which comprises passing an olefin cf the general (EH5 I CH2: GR

wherein R is selected from the group consisting of hydrogen and alkyl radicals of 1 to 5 carbons in the vapor phase admixed with oxygen over copper silicate as a catalyst at a temperature within the range of 275 to 35 0 C., and in the presence of sulfur as a promoter.

3; The process of claim 1 wherein the oxygen-olefin ,weight ratio varies from 0.01:1 to 7:1.

4. The process of claim 1 wherein the oxyg nl fin ht rati varies from 70:1 to :1.

5. The process of claim wherein the amount of said promoter incorporated in said reaction mixture is an amount varying from 0.01 to 2.0 grams per 2 liters of olefin said olefin measured under standard conditions.

6. The process of claim 1 wherein the amount of said promoter incorporated in said reaction mixture is an amount varying from 0.1 to 1.0 grams per 2 liters of olefin said olefin measured under standard conditions.

7. The process of claim 1 wherein the olefin is isobutylene.

8. The process of claim 1 wherein the olefin is propylene.

9. The process of claim 1 wherein the olefin is 2- methylbutene-l.

References Cited in the file of this patent UNITED STATES PATENTS Cheney et al Sept. 24, 1957 FOREIGN PATENTS Canada July 3, 1956 Great Britain Oct. 3, 1951 UNITED STATES PATENT OFFICE CE TIFICATE 0F CORRECTION Patent No, 3 ,,OO9 96O November 21 1961 Adolph C o Shotts eta].a

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5 line 1 after claim ineert 1 Signed and sealed thie 29th day of May 1962,

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A PROCESS FOR THE PREPARATION OF ALKYL SUBSTITUTED ACROLEINS WHICH COMPRISES PASSING AN OLEFIN OF THE GENERAL FORMULA: 